The present invention relates to an adjustable wrench, and more particularly to such an adjustable wrench which can be stably and conveniently adjusted to hold down any of a variety of bolts and nuts of different sizes.
A variety of wrenches have been disclosed for grasping and turning nuts, bolts, etc., and have appeared on the market. FIG. 1 shows a box end wrench according to the prior art. This structure of box end wrench has two boxes at both ends for grasping and turning nuts, bolts, etc. Because the work hole defined within each box of the box end wrench is not adjustable, the box at each end of the box end wrench is practical for grasping and turning only one Particular size of nuts, bolts, etc. In order to fit different sizes of nuts, bolts, etc., adjustable wrenches are developed.
FIGS. from 2 to 4 show three different structures of adjustable wrench. These adjustable wrenches commonly comprises a wrench body having a work head at one end defining a work hole, a movable pawl device mounted in the work head of the wrench body, and a nut mounted in a hole or open chamber on the work head of the wrench body and rotated to move the movable pawl device in or out of the work hole so as to grasp or release the workpiece.
The pawl device of the adjustable wrench shown in FIG. 2 has a circular chucking head. When the circular chucking head of the pawl device is Roved forwards and pressed against the periphery of the workpiece, only a part of the front chucking face of the circular chucking head is retained in close contact with the periphery of the workpiece, therefore the circular chucking head tends to slip on the periphery of the workpiece when the wrench is turned with the hand.
The adjustable wrench shown in FIG. 3 is not durable in use because the pawl device and the work head of the wrench body are disposed at different elevations. Furthermore, because the adjustment nut is disposed on the outside of the work head of the wrench body, it tends to be covered with rust.
The adjustable wrench shown in FIG. 4 is known in the prior art. However, this structure of adjustable wrench still has drawbacks. This structure of adjustable wrench is not practical for grasping and turning small nuts, bolts, etc., because the chucking head of the pawl device has a great thickness. Furthermore, because the chucking face of the chucking head of the pawl device has a smooth surface, the work head of the wrench body may slip on the periphery of the workpiece when the wrench is turned with the hand.
The present invention has been accomplished to provide an adjustable wrench which eliminates the aforesaid drawbacks. It is the main object of the present invention to provide an adjustable wrench which can be conveniently operated to positively grasp and turn different sizes of nuts, bolts, etc. According to one aspect of the present invention, the work head of the wrench body of the adjustable wrench has flat wall portions and teeth alternatively arranged with the work hole therein for acting with the pawl device to hold down the workpiece positively, and the pawl device has a substantially V-shaped chucking head comprised of a flat surface portion and a serrated portion moved with the pawl device to force the workpiece against the flat wall portions and teeth inside the work head of the wrench body, enabling the workpiece to be firmly secured to the work head of the wrench body and turned. According to another aspect of the present invention, the V-shaped chucking head has both ends slidably supported on two opposite side walls of the oval head of the wrench body by spring-supported steel balls. Therefore, the pawl device can be stably moved in and out of the work hole in the work head of the wrench body.